Room: Exhibit Hall | Forum 1
Purpose: Organ-based TCM has been purported to reduce organ dose to anteriorly-located, radiosensitive organs such as the breast. However, this reduction may come at the expense of increasing dose to other radiosensitive organs such as the lung. The purpose of this work was to compare lung and breast doses resulting from chest CT exams performed with an organ-based tube current modulation (TCM) to those resulting from exams using an estimate conventional attenuation-based TCM.
Methods: Under IRB approval, raw projection and image data were collected from eleven patients (7 males, 4 females) who underwent CT chest/abdomen/pelvis (CAP) examinations employing organ based TCM (XCARE + CAREDose4D, Siemens Healthineers, Forchheim, Germany). The TCM schemes for the chest portion were extracted from the raw projection data for each patient. Lung and glandular breast tissue were semi-automatically segmented from patient image data for each case to create voxelized models of patient anatomy for use in a validated Monte Carlo (MC) transport code. Additionally, for these patients, TCM schemes from conventional, attenuation-based modulation only (CAREDose4D) were also estimated using a recently developed method that accounts for patient attenuation characteristics and scanner machine limits. Absolute lung and breast doses for each TCM scenario were estimated for each patient model using a 128-slice MDCT source model in Monte Carlo simulations. The resulting lung and breast doses from each scheme were compared using within patient percent difference using the doses from organ-based TCM as the reference.
Results: With conventional attenuation-based modulation, the difference between lung dose across patients ranged from -11% to 59% while the breast dose across patients ranged from -5% to 127% relative to organ-based TCM.
Conclusion: Organ-based TCM can reduce breast dose when compared to conventional, attenuation-based TCM but may in turn increase lung dose in chest CT exams.
Funding Support, Disclosures, and Conflict of Interest: Michael McNitt-Gray, Ph.D Departmental master research agreement, Siemens Healthineers Dianna Cody, Ph.D Reviewer for the ACR CT accreditation program Research agreement with Gammex Rick Layman, Ph.D Research agreement, Siemens Healthineers